Fluorine-containing surfactants and fluorine-containing surface modifiers are excellent in, for example, leveling properties, wettability, penetrability, anti-blocking properties, slipping properties, water-oil repellency, and antifouling properties and hence are widely used for various coating materials, surface modifiers, and the like.
A cured coating film produced by applying and curing an active-energy-ray-curable coating material containing a fluorine-containing surfactant or a fluorine-containing surface modifier (hereafter, these are collectively referred to as just “fluorine-containing surfactant”) exhibits excellent antifouling properties. However, there is a problem that the antifouling properties of the surface of the cured coating film are degraded because the fluorine-containing surfactant is partially separated or evaporated from the surface of the cured coating film, during production steps of the cured coating film, by heating, wetting, exposure to a chemical agent such as an acid or an alkali, cleaning and wiping for removing fouling, or the like.
Specifically, for example, in the field of surface-treatment agents for protective films such as triacetylcellulose (hereafter, abbreviated as “TAC”) films in polarizing plates for liquid-crystal displays, to impart antifouling properties against fingerprints and fouling to the surfaces of films, the surfaces of the protective films are coated with ultraviolet-curable hard coating materials containing fluorine-containing surfactants and the like. However, in such a protective film, another surface with respect to the hard coating surface formed by application of a hard coating material is subjected to a saponification treatment (alkali treatment) for the purpose of imparting adhesion properties to the other surface. Accordingly, at this time, the alkali solution unavoidably comes into contact with the hard coating surface. The strong alkali solution washes off or decomposes a fluorine-containing surfactant and the like present in the hard coating surface. Thus, the fluorine-containing surfactant and the like are separated from the hard coating surface and antifouling properties are degraded, which, has been problematic.
Accordingly, a fluorine-containing surfactant that can withstand a saponification treatment has been proposed: the surfactant has a polymerizable functional group and is fixed in a cured coating film as a result of polymerization with another material. For example, a polymerizable fluorine-containing surfactant having an unsaturated group has been proposed, the surfactant being produced by copolymerizing a monoacrylate having a fluorinated alkyl group and an acrylic-based monomer having an active hydrogen and by subsequently causing the resultant polymer to react with an acrylic-based monomer having an isocyanate group (for example, refer to Patent Literature 1). This polymerizable fluorine-containing surfactant has a polymerizable group. When this surfactant is used as an additive to an active-energy-ray-curable composition, the surfactant forms covalent bonds with a polymerizable component in the composition and is fixed in the coating film. However, there is a problem that the antifouling properties are considerably degraded after a saponification treatment.
In addition, as with the above-described polymerizable fluorine-containing surfactant, a polymerizable fluorine-containing surfactant having a poly(perfluoroalkylene ether) chain and an unsaturated group has been proposed, the surfactant being produced from a material that is a compound having a (perfluoroalkylene ether) chain and di(meth)acryloyl groups at both ends of the chain (for example, refer to Patent Literature 2). Although the fluorine-containing surfactant having a poly(perfluoroalkylene ether) chain has high antifouling properties after a saponification treatment with respect to the surfactant described in Patent Literature 1, it does not satisfy antifouling requirements on a still higher level.
Accordingly, a material that maintains its very high antifouling properties even after being subjected to a saponification treatment has been demanded.